The etiology of the hepatic abnormalities observed after jejunoileal bypass (JIBP) for morbid obesity is unknown. Three factors individually or in combination may contribute to hepatic injury and dysfunction. These are: 1) Bacterial overgrowth in the bypassed small bowel, 2) Bile acid toxicity, 3) Protein malnutrition. The specific goals of the current investigation of the consequences of JIBP are as follows: 1) Document the occurrence of bacterial overgrowth in the small bowel and the anatomic and functional changes in the liver, 2) Determine if certain alterations in bile acid metabolism are present and if so, do these changes correlate to bacterial overgrowth, 3) Study the effects of antibiotic administration and prevention of protein malnutrition (by hyperalimentation) on liver histology and function. This problem will be studied using a canine model. We have chosen dogs since hepatic disease in dogs which closely resembles that seen in humans and small bowel bacterial overgrowth, always occurs following 80% or greater JIBP. The effects of administration of antibiotic and of supplemental parenteral amino acid solutions will be studied will be studied in order to determine if decrease in microbial content and improvement in protein malnutrition have any effect on the expected hepatic changes. To detect these effects a variety of postoperative studies including cultures of the small bowel, sequential analyses of bile acid patterns of bile and liver, repeated histological examinations of the liver and tests of injury and function of the liver will be done. It is hoped that clarification of the mechanism of this disturbing complication of JIBP will significantly contribute to: 1) the management of the problem when it occurs, or more ideally, 2) prevention by modification of the operation or the postoperative management.